Method and means for producing fogs, smokes, and insecticidal thermal aerosols



F. ANDREWS METHOD AND MEANS FOR PRODUCING FOG-S, SMOKES, AND

Oct. 9, 1956 INSECTICIDAL THERMAL AEROSOLS 3 Sheets-Sheet 1 Filed Aug. 7, 1952 E. F. ANDREWS 2,765,578 METHOD AND MEANS FOR PRODUCING FOGS, SMOKE-S, AND

INSECTICIDAL THERMAL AEROSOLS 3 Sheets-Sheet 2 Filed Aug. 7, 1952 jflweazeiw ddaMgw/fm Oct. 9, 1956 E. F. ANDREWS 2,765,578

METHOD AND MEANS FOR PRODUCING FOGS, SMQKES, AND INSECTICIDAL THERMAL AEROSOLS Filed Aug. 7, 1952 3 Sheets-Sheet 3 r/ w/em METHOD AND MEANS FOR PRODUCING FOGS, SMOKES, AND INSECTICIDAL THERMAL AEROSOLS Edward F. Andrews, Largo, Fla.

Application August 7, 1952, Serial No. 303,137

12 Claims. (Cl. 48-4259 This invention relates to method and means for producing fog or smoke, and to the method and apparatus for producing thermal aerosols carrying substances to be disseminated, such as insecticides.

A primary object of the invention is to provide an improved and simplified apparatus for producing fog, smoke, or substance distributing thermal aerosals which shall be compact, simple, economical, and eflicacious.

A further and more specific object is to provide such a fogger, equipped with a vaporizing or injector type of burner, which will provide its own forced draft of highly heated gas from which the oxygen has been completely or substantially burned out, which gases impinge upon, vaporize, and carry out the insecticidal fog oil, which is sprayed into a fog chamber, with heated walls, which discharges into the atmosphere.

Additional objects will appear from the following preliminary description.

By the word fogger is meant a device, such as described, for producing smoke, fog, or insecticidal aerosols, or the like.

Aerosols or fogs may be produced by the combination of atomization, heat, or fluid motion, more or less turbulent. The present invention utilizes heat and liquid atomization to a relatively greater extent, and will therefore operate efliciently with lower gaseous velocities in the region where the atomized fog oil mixes with the hot gases, that has been commonly employed in the past. This is highly advantageous, particularly for simple, cheap foggers, and for foggers to be utilized in the field or in locations where municipal electric power is not readily available. Foggers of the prior art, which employ high air or gas velocities to produce satisfactory fogs or aerosols, employ large air blowing or pumping devices supplying large volumes of air under considerable pressure, or at high velocity.

Foggers have also been mounted on airplanes flying at speeds in the vicinity of 100 miles per hour or more, and have utilized the pressure head corresponding to these speeds to produce high velocity air or gas flow.

In the first type of device, a large internal combustion engine of five or more horsepower, is commonly employed to run, for instance, a Roots blower. Devices of the second type are limited to use on airplanes moving rapidly through the air. Such engine driven devices are large, heavy, and expensive, and their maintenance and repair is costly. On the other hand, dependence on airplane flight speeds for high velocity air flow seriously limits the usefulness of such devices for many obvious reasons.

Other types of foggers of the prior art have the disadvantage, in addition to those previously mentioned, of being completely nonportable, are very heavy and bulky, and may be installed, for example, permanently below the surfaces of the ground. A purpose of such devices may be to produce smoke for signaling or indicating, and they would not be suitable for the mobile applications to which this invention is outstandingly adapted.

I have found that aerosols or fogs comparable or superior in quantity and quality to those produced by the costly and complicated devices above mentioned, can be produced by an inexpensive, small, light fogger which is easy and cheap to repair and maintain. Such a fogger may consist of a burner passage and combustion chamber comprising a thin metal shell lined with a refractory heat insulating material. Within the combustion chamber is a fog chamber made of a material which is strong and resistant to disintegration at high temperature, such, for instance, as stainless steel. This fog chamber is generally tubular, one end projecting out of the combustion chamber and open to the atmosphere. The other end, which is also open, is positioned adjacent the inner end of the combustion chamber so that there is a restricted passage for hot gases from the combustion chamber into this end of the fog chamber. The fog oil, with or without insecticide, is conveyed to this spray nozzle under moderate pressure and enters the fog chamber suitably as a conical finely divided spray. At the open end of the burner passage, a burner, suitably of the vaporizing injector type, directs its flame into the burner passage. The burner passage expands inwardly, slowing down and increasing the pressure of the gases from the burner jet.

The fuel supplied to the burner is suflicient to consume all or nearly all of the oxygen injected into the burner passage by the high velocity burner jet. Combustion is completed, or at least practically so, in the burner passage and combustion chamber, before the hot combustion gases pass through the restricted passage be tween the combustion chamber and the fog chamber. While passing through this restriction, the gases increase in speed and turbulence, and then combine with the fog oil spray from the spray nozzle. The spray is here formed into a fog or aerosol by contact with the hot gases and the walls of the fog chamber which are heated by the hot gases in the combustion chamber before they pass into the fog chamber. The fog or aerosol then passes out the end of the fog chamber open to the atmosphere, being cooled sufficiently to prevent their ignition by the fog oil spray and the cooler Walls of the fog chamber near the outlet before they encounter the outer air. With an inflammable fog oil, it has been found that the ignition of the fog or aerosol, when encountering the outer air, or in the fog chamber, can be effectively and reliably prevented by proportioning the area of the opening between the fog chamber and the combustion chamber properly with due regard to the amount of fuel supplied to the burner, the amount of air induced into the burner passage, and the amount of fog oil sprayed into the fog chamber. It is also desirable that the burner passage and combustion chamber be of suflicient length so that combustion is completed therein, and that the fog chamber be long axially compared'to its other dimensions. It is desirable also that the fog chamber be smaller at its outlet end than at the end adjacent the spray nozzle, and that the outlet end be sufficiently low so that any fog oil remaining in solid condition will run by gravity out the fog outlet. The fuel and fog oil may be supplied by air pressure in the respective containers. This small amount of air under moderate pressure may come from a small pump driven, for instance, from the fan belt of a jeep or other conveyance upon which the fogger is mounted. In fact, the power required for supplying sufficient compressed air is so small that it may even be supplied by a hand pump, operated intermittently, if the capacity of the fogger is not excessive. When the pump delivers a small excess of air, a very uniform air pressure may be maintained by a relief valve through which the excess air is discharged when the pressure exceeds a predetermined value.

As an alternative to the arrangement above described, a nonvaporizing type of burner to which air is supplied by a small electric motor driven blower, may be employed instead of the vaporizing burner. Two small centrifugal pumps driven from the motor shaft may supply the fuel and insecticide from their respective tanks from which liquid is supplied to the pumps by gravity. If smoke, as ditferentiated from an insecticide bearing aerosol, is to be produced, only one pump and one tank may be required. The motor driving the pump may be a 6-volt electric motor supplied with current from the storage battery and generator of the jeep or other automotive vehicle which carries the fogger. Although an air blowing motor is required in this latter modification, it may be a small and inexpensive one, and so ditfers markedly from the large engines, motors, or the like, required by devices of the prior art.

Still further objects and advantages will become apparent from the more detailed description which follows.

In the drawings:

Fig. l is a generally illustrative diagrammatic view showing the elements of the fogger of my invention in a very simple form;

Fig. 2 is similar to Fig. l, with the combustion chamber slanted upward relative to the burner passage. A further axial extension of the combustion and fog chambers is shown in dotted lines;

Fig. 3 is a longitudinal cross section of a complete fogger of suitable form;

Fig. 4 is a cross section, taken on the line 44 of Fig. 3;

Fig. 5 is a diagrammatic view showing the fuel and insecticide supply system connected to the fogger of Fig. 3, constituting a complete fogger system with vaporizer injector burner; and

Fig. 6 is a diagrammatic modification illustrating the application of a motor driven blower type burner instead of the injector burner, to the fogger shown in Fig. 3.

In Fig. 1, the combustion chamber a is simply an extension of the burner passage b, there being no separation or discontinuity between the two. The combustion chamber ends in a solid wall and the fog chamber d passes out through the bottom wall of the combustion chamber.

The spray nozzle e is mounted at the upper end of the spray cone 1. The fog chamber is tapered from a relatively small outlet at the lower end to a larger diameter at the inner end, which is positioned adjacent the upper wall of the combustion chamber to form, with this wall. a restricted gas passage between the combustion chamber and the fog chamber. One purpose of the spray cone 1 is to position the spray nozzle far enough from the fog chamber so that the conical spray does not impinge against the walls of the fog chamber, until it has expanded sufiiciently to allow good atomization, and so that impingement takes place adjacent the large end of the fog chamber where the area of impingement of the spray on the fog chamber is relatively large.

The outline of the conical spray and its impingement on the fog chamber is shown by the dotted lines g.

The burner It may be of the vaporizer injector type, as shown more in detail in Figs. 3 and 5. The high velocity discharge from the burner 11 induces a high velocity flow of air into the burner passage a. The expanding burner passage constitutes a diffuser which reduces the velocity and increases the pressure of the moving gases. These pass through the restricted annular passage 1' and mix with the fog oil spray in the fog chamber a, passing out the fog chamber outlet j. If desired, the burner passage a may be offset to one side of the vertical central plane of the fog chamber so that the gases from the burner passage tend to whirl around the fog chamber and produce a whirling flow through the restricted passage i.

A separating abutment may be placed in the large end of burner passage a as shown in Fig. 3, so as to cause the gases to separate into two streams which pass around the fog chamber in opposite directions. This has the advantage of more equal heat distribution around the periphery of the fog chamber, which is desirable to avoid hot spots tending to cause deterioration of the walls ot the fog chamber. Hot spots may also cause additional carbonization or decomposition of the spray liquid, espeeially when containing insecticide.

Fig. 1 illustrates one of the simplest and most elcmentary forms of this type of fogger. It is characterized. however, by being quite long. Also, the fog outlet j is considerably below the burner passage a, so that there is no natural draft from inlet to outlet. On the other hand, if the outlet j were placed on top, any fog oil residue remaining liquid would run into the combustion chamber instead of out the outlet. This may be nudesirable.

Pig. 2 shows an arrangement quite similar to Fig. l. in which the same letters designate corresponding parts. However, the combustion chamber b joins the burner passage a at an angle more or less approaching a right angle. It will be apparent that this reduces the overall length of the fogger for the same length of kite-trial gas passage. it also positions the fog chamber a" in a more nearly horizontal position, but still with its outlet j below its large end so that residual liquid fog oil will drain out. The outlet j is also somewhat above the burner passage a so that some natural draft is provided. in addition, the corner juncture it between the burner pass and the combustion chamber acts somewhat as a shield to prevent the direct passage of the flame from the burner passage into the restricted passage 1'.

The dotted lines in Fig. 2 show the extension of the combustion chamber upward and to the left, to provide a combustion chamber I) substantially longer axially than the height of the burner passage 1:. This still further increases the length of the internal gas passage for a given overall length of the device. it also increases the length of the fog chamber and the length of contact between the gases in the combustion chamber and the outside of thrfog chamber. It will be apaprent that the 35221118 increase in the length of the combustion chamber 11 to the height of the burner passage a could be cficetcd in Fig. l, i." desired, with similar results.

Fig. 3 shows a complete foggcr of a similar type to that shown partially in dotted lines in Fig. 2, and will now be described in greater detail.

The burner passage 16 has a flared circular opening 11 and expands inwardly both in a horizontal and vertical direction, providing a diffuser which reduces the velocity and raises the pressure of the gases. The burner passage 10 may be made a separate piece with relation to the combustion chamber .12, the dividing line between the two parts being along the diagonal line 13. This permits the cores employed for casting the refractory lining to be withdrawn to the right from the burner passage 10, and straight downwardly from the combustion chamber 12. it may be pointed out here that the main body of the foggcr as a whole consists of a sheet metal shell lined with and forming the outer protective housing for the refractory lining 15. The outer shell or housing 14 may be mad.- of a strong noncorrosive metallic material. capable of withstanding moderately high temperatures, for example. galvanized or aluminized sheet steel, or a stainless steel. where higher cost may be tolerated.

The refractory lining 15 may consist of such castable refractory materials as LWl castable refractory cement, or Tufllight made by Plibrico Company of Chicago, where a fairly thick lining is employed as shown in Fig. 3. When lightness or compactness become of greater importance, and where greater heat losses may be tolerated,

thinner linings may be employed and in this case it is desirable that the lining material have considerable strength and resistance to cracking and flaking. It is desirable that the lining material have good heat insulating qualities as well as ability to withstand high temperatures, especially in the region of direct flame impingement. When a castable material such as above mentioned is employed, cores consisting of sheet metal held together by screws, or other means removable from the inside, may be employed to form the hollow interior constituting the burner passage 10, the combustion chamber 12 and the double passage 16 connecting the two. The two cores for this double passage may fit at the combustion chamber end into appropriate slots in the cylindrical combustion chamber core, and into openings in a core plate which is positioned along the diagonal line when the combustion chamber unit is being cast. This is removed after the lining has set and after the two rectangular cores forming the double passage 16 have been collapsed and removed. Thus, an abutment 17 of refractory material is provided which strengthens the lining, minimizes hot spots by providing better heat distribution around the fog chamber 18, and provides more highly heated surface in the path of the flame to expedite completion of combustion.

From the double passage 16, the hot combustion gases flow into the main bore of the combustion chamber 12, around the fog chamber 18, and back to the left toward the larger or left end of the fog chamber 18. The left or spray nozzle end of the combustion chamber comprises a removable cover 19 having an outer cover 20 and a refractory lining 21. A spray core 22 is secured to an outwardly projecting flange on the cover 20, for instance, by means of self-tapping screws. The refractory lining surrounds and also tends to hold the spray cone 22. The spray nozzle plate 24 is attached to the small end of the spray cone, for instance by welding or silver soldering.

The removable cover 20 may be fastened to the outer shell 14, for instance, by circumferentially spaced angles 25 screwed to the shell 14.

The fog chamber 18 may consist of a rolled up sheet metal tube having a seam located along the top side, where there is the minimum tendency for leakage of solid fog oil in the event the seam is not perfectly tight. It may be made of 16 or 18-gauge stainless steel, for instance 18% chromium and 8% nickel. Higher chromium stainless steels without nickel or other heat and corrosion resistant materials may also be employed. The fog chamber 18 may be held in a conical closely fitting metal sleeve 26 which in turn is held, for example, by spot welding, to the outlet cone 27 at the annular juncture 28. The outlet cone 27 may be secured to the outer shell 14 by means of a circle of annularly spaced lugs riveted to the inside of the shell 14, and a corresponding number of screws passing through the outwardly projecting flange at the big end of the outlet cone 27 and engaging threads on the corresponding lugs 22. This outlet cone 27 may also be spot or otherwise welded to the shell 14, if desired. The fog chamber 13 may be secured to the conical supporting member 26 and to the outlet cone 27 by means of three screws 28a passing through the annular juncture 28 of the two last mentioned members. As these screws pass through the walls of the fog chamber, it is preferable that they be confined to the upper half of the fog chamber so that no holes pass through the bottom of the fog chamber where liquid fog oil might leak.

The supporting cone 26 is held firmly in place by the refractory lining which surrounds it as shown in Fig. 3. By removing the three above mentioned screws holding the fog chamber, and by removing the cover 20, the fog chamber can be taken out by sliding it out of the combustion chamber to the left.

An additional protective cone 30 may be provided to surround the outer wall of the fog chamber 18 toward the outlet end of the combustion chamber. The purpose of this is to protect the walls of the fog chamber against deterioration by the combustion gases which have the highest temperature in this area. It also will further reduce the development of hot spots. If the protective cone 30 deteriorates under the heat, it may be replaced at a much smaller cost than replacing the whole fog chamber. It may also be made of a more heat and corrosion resistant material even than the fog chamber, as the quantity required is relatively small.

The fog chamberis positioned relative to the inner surface of the cover lining 21 so as to provide an annular gap 31 between the large end of the fog chamber and the cover lining. This annular gap 31 constitutes a separation of restricted area between the inside of the fog chamber 13 and the combustion chamber 12. As has previously been pointed out, the area of this annular gap 31 is important to the proper functioning of the fogger. If it is too large and if an inflammable fog oil, such for instance, as No. 2 furnace oil, is employed, excess oxygen may pass into the fog chamber 18 and tend to cause internal burning or even ignition of the fog at the fog chamber outlet 32. If desired, louvers 33 may be formed in the large end of the fog chamber 18 to give the gases flowing through the annular gap 31 a rotary or whirling motion. These louvers may be made by slotting the large end of the fog chamber and bending one of the slotted edges inwardly. It should be noted that the same.

edge should be bent inwardly on all of the slots, which may be, for instance, six or more in number, so that they will all tend to produce a swirl in the same direction.

The fog oil spray nozzle 34 passes through a hole in the spray nozzle plate 24 and may be secured to it by means of screws 35'. The spray nozzle 34 may be of the type having a central outlet aperture and a whirl chamber in which the fog oil whirls rapidly as it passes out of the outlet aperture, thus forming a hollow conical spray effectively atomizing the fog oil. It is desirable to let this spray cone expand considerably before striking any obstruction.

By providing a spray cone 22 of suitable axial length and diameter with respect to the diameter and position of the large end of the fog chamber 18, the conical spray from the nozzle 34 travels a considerable distance through the heated gases before impinging upon the inner fog chamber wall close to, but still substantially within, its largest diameter. The outer end of the spray cone 22 being uninsulated and exposed to the outer air, also tends to keep the spray nozzle 34 relatively cool.

Although the annular gap 31 must not be too large, for reasons previously stated, it must still be large enough to supply sufiicient flow of hot gases to mix with and carry the fog oil spray out of the fog outlet 32 with adequate speed of flow. It has been found that too small an annular gap also tends to cause ignition at the fog outlet 32, as Well as a reduction of the quantity of fog oil which can be effectively converted to fog or aerosol. It is desirable that the outlet end of the fog chamber 32 be substantially lower than the larger inner end so that any residual liquid fog oil will drain out of the outlet 32 instead of back into the combustion chamber. This slope toward the outlet end 32 of the fogger should be great enough to allow for changes in the level of the fogger which may occur if the vehicle on which it is mounted runs momentarily over an inclined surface, and should also be sufiicient to overcome obstructions resuling from carbon or tar deposits on the inside of the fog chamber.

The fogger may be mounted, for instance at three points, on legs formed as part of or attached to the outer shell 14. Two of these legs or support points 36 are located at the outlet end of the combustion chamber unit, and a third, 37, may be positioned at the inlet end of the burner passage 10. A burner suppont member 38,

' 7 formed of a sheet metal channel, may be attached to the inlet end of the shell surrounding the burner passage 10.

The burner 39 may be mounted on the outer end of the member 38 by means of a pivot bearing 40 around which the burner may be rotated into alignment to direct the flame into the burner passage 10, or out of alignment to direct the flame out of and away from the burner passage when the fog oil supply from the connection 41 is turned off, by means of the fog oil valve 42. To provide additional strength and rigidity, an upper burner rearing 4-3 i carried by an upper burner bearing support member 44 secured to the top of the shell surrounding the burner passage 10.

The burner 39 is provided with a vaporizing coil 45. Fuel, such as kerosene, is supplied to the vaporizing coil 45 through the vertical fuel pipe 46. This passes through and is guided in the upper bearing 4-3. The fuel pipe 46 carries a bevel gear 47. This meshes with a second bevel gear 48 which is carried on a control shaft 3 having a bearing 50 in the upper suppont member 44. This control shaft 49 has a control knob 51 at its opposite end located within convenient reach of the driver of the jeep or other vehicle which may carry the fogger. By turning the knob 51 in one direction or the other, the burner can be caused to supply heat to the fogger, or the heat supply to it may be interrupted, as desired.

As the vaporizer injector type of burner here shown requires generation, the fuel supply to the burner cannot be cut olf by means of the Valve 52 if it is desired to cut off the heat supply temporarily. If this were done for any very extended period, the burner would cool down and would have to have its vaporizing coil 39 reheated before it could be fired again. Therefore, the valve 52 is only employed to cut off the fuel supply from the connection 53 when fogging operations have been completed.

The fog oil supply is controlled by the control wheel 54 which is likewise positioned within convenient reach of the driver, and is connected to the fog oil cutotf valve 42 by means of a tubular shaft 55 with a universal joint 56. If the shaft 55 cannot run coaxially with the stem of the valve 4-2, one or more corresponding universal joints may also be included in the shaft 55 and also in the shaft 49, if desired.

Fig. 4 is a cross section of the embodiment taken along the line 44- of Fig. 3. The separating abutment 17 between the two passages 16 connecting the burner passage 16 with the annular combustion chamber 12, is clearly shown. The flared annular opening ill of the burner passage 10, and the manner in which this annular opening 11 expands to a rectangular passage larger in both dimensions than the opening 11, is also clearly shown. The expanding taper of this difiuser passage should preferably not greatly exceed a seven degree angle for maximum diffuser efliciency. It will be seen from Fig. 4 that the walls of the fog chamber 18 are suitably made concentric with the inner surface of the refractory lining of the combustion chamber 12. The spray cone and the spray nozzle are also suitably concentric with the fog chamber 18, as is also the supporting cone 26 at the opposite end of the fog chamber. The supporting cone 26 and the protective cone 36 are appropriately tapered closely to fit the outside of the tapered fog chamber 18.

Referring to Fig. 5, the burner shown there, and also in Fig. 3, is of the vaporizer injector type. The fuel supplied from the fuel pipe 4-6 to the vaporizer coil 45 is vaporized in the coil 45 from the heat of the burner 39. The fuel oil vapor passes from the hot end of the coil 45 through the vapor tube 57, which is a continuation of the coil 4-5, to the burner jet orifice plug 58. This is preferably a removable steel plug having a concentric orifice of proper size, which directs a jet of fuel vapor through the center of the vaporizer and into the center of the burner passage 10. This plug 58 may be readily changed and replaced by another plug havinga larger or smaller 8 orifice as desired. The size of the orifice in the plug 58, together with the adjustment of the valve 52, aifects the character of the combustion and the operation of the fogger, as will be later described.

The combination of the burner jet and the diffuser type burner passage 10 constitutes an injector ram jet combination which is capable of producing a continuous and fairly rapid gaseous flow into the annular burner passage opening 11 through the burner passages 16 into the combustion chamber 12, through the annular gap 31, through the fog chamber 3.8, and out of the outlet 32, Without requiring any blower or outside air velocity. This is be lieved to be a very simple and effective way of supplying an adequate flow of hot gases from which the free oxygen has been substantially burned out. This is a novel hot gas moving means for the simple, efficient, and economical production of very adequate quantities of fog and especially insecticidal thermal aerosols.

Fig. 5 shows a complete fogging apparatus utilizing the fogger unit of Fig. 3. This system may be employed as shown, for producing insecticidal thermal aerosols with a vaporizer injector burner. Corresponding parts have the same numbers as employed in Figs. 3 and 4.

Fuel tank 59 may contain, for instance, white kerosene. This is supplied to the burner through the connecting pipe 53 which runs close to the bottom of the tank 59. The air compressor 60, which is shown as a reciprocating air pump driven by a belt 61 connected to an appropriate pulley on the jeep or other vehicle carrying the fogger, supplies air pressure to the fuel tank 59 and the insecticidal fog oil tank 62 through the air sup ply pipe 63 and the connecting pipe 64. Other types of air or gas supply might be employed, such as a rotary compressor or a compressed air or gas tank. Even a hand pump of comparatively long stroke may, in some instances, be employed. A pressure relief valve 65 may be included in the line and the pump may supply an excess of air. Thus, a constant pressure is maintained on the tank 59 and 62, and the excess air is discharged to the atmosphere through the valve when the predetermined pressure is exceeded. When a hand pump is employed, pressure may be readily controlled by a pressure gauge, by which the operator determines the necessary operation of the pump. It has been found that quite a wide range of pressures maybe employed, depending upon the results desired, but a pressure of 20 to 50 pounds has been found satisfactory for certain purposes.

As will be seen, the air supply pipes 63 and 64 connect to the top of the tanks 62 and 59, so as to put air pressure above the liquid in these tanks. The outlet pipe from these tanks are at the bottom so that fuel is forced out by the air pressure.

As described in connection with Fig. 3, the line 41 supplies insecticidal fog oil to the spray nozzle 34 and the line 53 supplies fuel oil to the orifice plug 58. In the event that the same liquid can be employed, both as fuel and fog oil, one of the tanks shown in Fig. 5 may be dispensed With, and the spray nozzle 34 and the orifice plug 58 may be supplied from the same liquid supply source. However, the fogger of this invention provides additional important advantages over previous devices for supplying insecticidal aerosols where the insecticidal fog oil is separate from and different than the burner fuel.

Where relatively expensive insecticides are carried by the fog oil, it is very important to avoid any burning in the fog chamber, as this may destroy and waste the insecticide. The effectiveness with which the combustion can be confined to the combustion chamber and prevented in the fog chamber with a fogger of this invention is, therefore, of special advantage where a separate tank containing expensive insecticide is employed in addition to the tank containing the cheaper fuel, which latter alone should be burned. This is of lesser impor- Eance where a fog oil as cheap as the fuel provides the Fig. 6 shows an alternate type of burner and fuel supply which may be employed where a power source, such as a small electric motor, may be employed. This system may be employed with the fogger of Fig. 3, and is shown connected to the burner passage 10 of Fig. 3. The blower 200 may be of the centrifugal type and has an air intake 201 and an air discharge passage 202 which connects directly to the annular opening 11 in the burner passage 10. The impeller of the blower 200 may be mounted directly on the shaft of a small electric motor 203. This motor may be driven from the electrical system of the jeep or other vehicle carrying the fogger. A fuel tank 159 has a gravity outlet connected through a shutoff valve to the fuel supply line 204. This line connects to the inlet of a fuel pump 205 which may be of the centrifugal type. The fuel outlet of this pump connects through the line 153 to the fuel atomizing nozzle 158. The insecticide tank 162 also has a gravity fed line 208 with a shutoff valve, which line connects to the intake of a fog oil pump 209. This delivers fog oil through the line 141 to the fog oil spray nozzle 34 shown in Fig. 3. The fuel pump 205 and the fog oil pump 209 may have centrifugal impellers which may be mounted on an extension of the shaft of the motor 203. These centrifugal pumps may be constructed so that at the speed at which they are driven by the motor 203, they will produce the desired pressure of fuel at the spray nozzle 34 and the fuel spray nozzle 158. If rotary positive pressure pumps should be employed, pressure regulating valves may be provided.

In this embodiment, the air flow through the fogger is provided by the blower 200. An electric igniter 210 may be provided to ignite the fuel-air mixture near the entrance to the burner passage 10 when the motor 203 is started. The system as shown in Fig. has the advantage of a burner which may be extinguished and relit at any time after being stopped, by means of an electric spark without requiring generation. It also permits the use of fuel tanks which do not have to withstand pressures such as are employed in the system of Fig. 5.

The tanks of Fig. 6, which are vented to the atmosphere, are also more easily refilled and can be of lighter construction. However, blowers and pumps with a suitable power source for driving them (with their attendant cost and complications) must be employed which are not required in the system shown in Fig. 5. The advantage of the system of Fig. 5 or Fig. 6, may vary with the capacity and use of the foggers. For instance, for a small hand-operated device, the injector burner system of Fig. 5 would be strongly preferred, as it would be also for a large capacity fogger requiring an extra engine to operate the blower of Fig. 6.

The operation of the fogger of this invention, as illustrated in Figs. 3, 4, and 5, is as follows:

First the pump 60 is operated until adequate pressure is provided on the fuel and insecticide tanks 59 and 62. Then the burner 39 is generated by partially opening the valve 52 and running fuel oil into the generating pan 66. This is then ignited and when the vaporizer 45 has been heated, the valve 52 is opened to the proper amount and the burner is in full operation. Prior to generation, the burner should be turned to the nonheating position by the knob 51 so that the flame is not directed into the burner passage until it is in full operation. The knob 51 is then turned in the opposite direction, and the flame of the burner is directed into the burner passage. An appropriate time is then allowed to elapse for the fogger to be brought up to proper operating temperature. This length of time depends on the thickness of the lining and other factors which may vary in different types. A five or ten minute interval may be sufficient. The wheel 54 is then turned to open the valve so that the conical fog oil spray discharges into the large end of the fog chamber. The fogger is then in complete operation, and heavy clouds of fog or aerosol issue from the opening 32. The fog oil spray being directed toward the outlet of the fog chamber, imparts additional acceleration to the flow of gases therethrough. It is desirable for the opening 32 to be of considerably smaller diameter than the large end of the fog chamber, and the fog is accelerated as it passes out of the opening 32 and is directed downwardly and rearwardly thereby.

In some cases, it may be desirable further to restrict the opening 32, which may be done, for instance, by a diagonal baflle at the fog outlet, as shown in dotted lines in Fig. 3. This baffie should be at the top of the fog chamber so as not to obstruct the drainage of unvaporized fog oil, if any, from the outlet.

During the operation of the fogger, the pump 60 should operate continuously, or at least intermittently. However, the air required is only suflicient to displace the fuel and insecticide used, and a very small pump is sufficient for a fogger of considerable capacity. If the tanks are not too full, the pressure above the fuel will operate the fogger for a considerable length of time.

To cut off the fog, the valve 42 is first closed and after a short interval the knob 51 is rotated to turn the burner flame out of the burner passage to avoid overheating of the fogger, which will occur if the fog oil supply is turned off and the burner is left directed into the burner passage. However, the burner should not be turned away from the burner passage until after the fog oil has been shut off, as in this case air from which the oxygen has not been burned out will enter the fog chamber and ignition in the fog chamber is likely to occur. If fogging is to be resumed, the burner is first turned back into the passage so that oxygen depleted gas flow is established before the fog oil spray is turned on.

For one form of mosquito or other insect control, the

fogger may be mounted With the outlet 32 projecting rear-.

wardly and slightly to the right from the rear of a jeep or other conveyance, which may then run up and down the streets projecting the fog backward and to the right. This operation is performed preferably when there is little or no wind and no excessive rising air currents. A fogger of this type which will fog 15 to 20 gallons of No. 2 furnace oil containing somewhat less than a pound of DDT per gallon, may be approximately three feet long, about a foot and a half'high, and one foot wide, and may weigh from 50 to pounds, or even less.

Using a spray nozzle 34 delivering about 18 gallons per hour, a burner orifice plug 58 having an orifice the size of a No. 58 drill, may be employed, with pressure of about 50 pounds on both fuel and fog oil. A suitable fog chamber would be from seven to eight inches in diameter at the large end, and four to live inches in diameter at the small end. Gperation appears to be aided under certa-in circumstances by the baffle 67 restricting the outlet opening 32. With these proportions, the annular gap .31 operates well if the gap is about -three-fourths of an inch to an inch wide. Good operation is secured when the orifice of the spray nozzle 34 is about six or seven inches away from the point of impingement between the conical spray and the wall of the fog chamber 18.

The circular opening 11 operates Well when it has a diameter of about four inches and the end of the vaporize-r 45 is located about two inches to the rear thereof. Some extension of the fog chamber beyond the refractory insulating material inside the annular joint 28 appears desirable to reduce the temperature of the fog somewhat be fore it encounters the oxygen of the outside air. In proportioning the area of the various passages, it may be borne in mind that the air at the inlet 11 is relatively cool. This is heated up in the combustion chamber and its volume increased. This volume contracts somewhat as a result of the cooling effect of the fog oil spray. The velocity tends to be high at the annular gap 31, because the area is relatively small and the volume quite large.

The area of the outlet passage 32 may be somewhat smaller than the effective area of the annular gap 31. It is believed that the nature of the surface of the fog chamber where the spray impinges, and beyond, is a factor in the efiicient production of fog or aerosol. If this surface is rough, or of such a nature as to be more readily wet by the spray, better operation seems to result. It is desirable to avoid the formation of sizable liquid drops which tend to vaporize slowly.

When DDT is used as an insecticide, a certa n amount of carbonization may occur inside the fog chamber. This can be cleaned out, however, after an hour or two of fogging, by inserting a small metal hoe into the opening 32 and scraping out the deposits.

The operation of the embodiment shown in Fig. 6 is similar to that above described, except that the device is turned on and off by stopping and starting the motor 283. in order to warm up the fogger when starting, the valve to the fog oil tank 162 may be closed, thus cutting off insecticide supply until this valve is opened after the fogger has come up to proper operating temperature. If the same oil is used for fog and fuel, a single pump may be employed, as described in connection with Fig. 5. The igniter may be arranged to be operated at the same time that the motor is turned on, and in fact may utilize the same current which energizes the motor.

Although only one type of operation has here been described in detail, there are many other applications for the device of this invention which will be apparent to those skilled in the art.

Having thus described my invention, What I claim as new and desire to secure by Letters Patent of the United tates, is:

1. A fogging apparatus comprising a closed housing having a heat inlet in a side wall adjacent one end thereof, an open ended fog chamber in said housing having side walls spaced from the side walls of said housing, one open end of said fog chamber being spaced from the end of said housing opposite said heat inlet, to form a restricted gap connecting the interior of said housing with the interior of said fog chamber, the other open end of said fog chamber passing through the end wall of said housing, means to introduce fog forming material into said fog chamber and, burner means causing a flow of hot gases through said heat inlet between the inner wall of said housing and the outer wall of said fog chamber and hrough said restricted gap with increased velocity to the inside of said fog chamber where said hot gases mingle with said fog forming material introduced by last said means, the resulting mixture being expelled as fog from the outer end of the fog chamber.

2. Fogging apparatus including a housing having an inlet for hot combustion gases adjacent one end, burner means supplying said hot gases, a fog chamber within said housing having gas passage means at one end communieating with said housing, a fog outlet at the other end of the fog chamber, communicating with the atmosphere whereby said combustion gases flow through said housing on the outside of the fog chamber into the fog chamber and in the opposite direction through the fog chamber outlet to the atmosphere, and means to introduce fog material into said fog chamber.

3. A fogger comprising a walled housing defining a gas passage having a burner inlet at one end and afog outlet at the other end, a vaporizing injector burner preheated for starting directed into said burner inlet to establish a flow of heated combustion gases through said housing and out said fog outlet, means located intermediate the ends of said housing introducing a fog producing substance into said housing for conversion to fog and expulsion from said fog outlet by said hot gas flow, means to interrupt the fogging operation and means for interrupting the heat supply from said burner to said burner inlet while maintaining said burner preheated and ready to resume full heat supply to said burner inlet.

4. A fogger comprising a hot gas duct having a burner inlet and a gas outlet, a burner, a source of liquid fuel, means supplying vaporized liquid fuel from said source under pressure to said burner, nozzle means in said burner delivering a jet of vaporized fuel under pressure into the burner end of said duct to induce the fiow air into said duct and expel combustion gases from said gas outlet, a source of vaporizable liquid, a second jet nozzle means adjacent said gas outlet, and means for deliverinq said vaporizable liquid under pressure from said source to said second jet nozzle means.

5. A fogging apparatus including a duct defining a gas passage having an air inlet end and a fog outlet end, a source of liquid fuel, a vaporizer at said inlet end, means supplying liquid under pressure from said source to said vaporizer, nozzle means connected to said vaporizer discharging vapor under pressure in a high velocity jet past said vaporizer into said duct where combustion is completed and a flow of air and heated gas is induced by said jet, and means located adjacent said outlet end directing a fog producing substance into the stream of hot gas in the direction of said flow so as to augment the flow and convert the said fog producing substance into minute particles.

6. A fogging apparatus including a housing having an air inlet, a burner including a source of liquid fuel under pressure and a vaporizer supplied therefrom directing a jet of vaporized fuel and injecting air into said housing, means for causing combustion of said fuel and air which combustion supplies heat to the vaporizer and to the gas stream flowing through the housing, a fog outlet in said housing, a source of vaporizable liquid under pressure, and means directing a jet of said vaporizable liquid into said housing directed toward said outlet whereby the injector effect of said burner and the velocity of said outwardly directed vaporizable liquid produces a flow of hot gases and heated fog from said outlet.

7. In a fogging apparatus two liquid sources, pump .reans applying pressure to liquid from said sources, a combustion duct having an air inlet at one end and a gas outlet at the other, a vaporizer at said inlet end, means supplying liquid under pressure from one of said sources to said vaporizer, nozzle means connected to said vaporizer discharging vapor under pressure in a high velocity jet past said vaporizer into said duct where combustion is completed and a flow of air and heated gas is induced by said jet, and means within said duct supplied with liquid under pressure from said other source directing a second jet toward said outlet end augmenting the flow of combustion gas and air in said duct and expelling aerosol fog.

8. The method of producing a thermal aerosol comprising the steps of applying pressure to a liquid fuel, applying heat thereto to cause vaporization and an increase of volume inducing a flow of air into a zone by directing a high velocity jet of said vaporized fuel under pressure into the inlet end of the zone so as to inject air therein, burning the injected fuel air mixture in the zone and introducing aerosol forming material into the hot combustion gases so as to augment the flow of said gases, and effect the discharge of a finely divided aerosol fog from the outlet end of the zone.

9. A fogger including a walled combustion chamber having a fluid injection opening at one end and a fog chamber opening at the other end, an open ended fog chamber located in spaced internal relation to said combustion chamber and extending out of said fog chamber opening, the inner end of said fog chamber and the adjacent wall of the combustion chamber forming passage means of restricted area connecting said combustion chamber with the inside of said fog chamber, and fluid injection means for injecting fog forming material through said fluid injection opening into the inner end of said fog chamber, and said combustion chamber having a burner opening through which hot gases are introduced so as to surround and enter said fog chamber through said passage means of restricted area, thereafter engaging said fog forming material which is carried out of the other end of said fog chamber by the flow of said hot gases.

10. A fogging apparatus including a hot gas duct having an air inlet and a hot gas outlet, a source of liquid fuel under pressure, means for vaporizing said liquid fuel, a burner having a nozzle, connecting means supplying vaporized fuel from said source to said nozzle from which it is discharged in a high velocity jet into the inlet end of said duct in Which the fuel is burned and inducing a flow of air and hot gases in said duct, and means located adjacent said outlet and directing a vapor-producing substance into the stream of hot gas in the direction of said flow so as to augment the flow and expel the vapor-producing substance from said hot gas outlet to produce an aerosol fog.

11. In a fogging apparatus, two separate liquid sources, means for pressurizing the liquid from said sources, a combustion duct having an air inlet at one end and a hot gas outlet at the other end, means for vaporizing the liquid associated with one of said sources, a burner having a nozzle means connected to said one liquid source discharging vaporized liquid under pressure in a high velocity jet into the air inlet end of said duct Where combustion is completed and a flow of air and heated gas is induced in said duct by said jet, and mean-s adjacent the outlet end of said duct supplied with liquid under pressure from said other source directing a second jet out 14 said outlet end augmenting the flow of combustion gas and air in said duct and expelling aerosol fog.

12. The method of producing a thermal aerosol comprising the steps of pressurizing a liquid fuel, supplying heat thereto to cause vaporization inducing a flow of air into a passage by directing a jet of vaporized fuel under pressure into the inlet end of the passage so as to inject air therein, burning the injected fuel-air mixture in the passage to produce a flow of hot gases through and out of said passage, and introducing a second jet of fluid moving in the same direction into the hot combustion gases to augment the flow of said gases and to form a finely divided aerosol fog at the outlet of said passage.

References Cited in the file of this patent UNITED STATES PATENTS 473,165 Russell Apr. 19, 1892 813,374 Gilbert Feb. 20, 1906 2,458,541 Urquhart Jan. 11, 1949 2,500,787 Lelgemann Mar. 14, 1950 2,606,604 Witherell Aug. 12, 1952 2,611,992 Loy et al. Sept. 30, 1952 OTHER REFERENCES Karcher: German patent application 138,004, Feb. 25, 1943. Published June 11, 1948 (Frames 8907-8911, Reel 83, 291). Ofiice of Technical Services Release. 

